Based on the progress in chemistry and the evolution in process design cleaning processes has increased in performance particularly over the last decades. New detergent formulations and highly task specific machines has come to market, rendering the overall cleaning processes very efficient and more environmentally friendly. Nevertheless, also the standards for process definition and reproducibility evolved, increasing the burden of documentation. Especially, for GMP-regulated industry sectors there is a high demand for significant process parameter in the field of cleaning, which are able to provide more reliable process information besides the “visually clean” condition provided by the standard.
Several different solutions for the assessment of cleaning performance have been proposed in the area of sterilization, wherein the absolute level of contamination after the process as well as the reduction ability is a critical process parameter. For monitoring purposes the literature propose either to examine directly the status of the surface of items subjected to the cleaning process or to use “artificial” test devices, which are introduced into the process additionally to the items to be cleaned. The latter variant is able to provide reproducible test standards and is more flexible, because different aspects of the cleaning process can be monitored as a function of the test device design.
WO 2014/137540 A1 for instance disclose a method of colorimetrically determining a concentration of at least one chemical species in a liquid medium, the method comprising: providing a chemical test strip having a reactive zone; providing an imaging device and image analyzing software; exposing the reactive zone to at least a portion of the liquid medium thereby creating a post-exposure reactive zone; imaging the post-exposure reactive zone using the imaging device thereby creating a digital image of the post-exposure reactive zone; optionally cropping the digital image of the post-exposure reactive zone to isolate a portion of the digital image for analysis; analyzing at least one colorimetric parameter of at least the portion of the digital image of the post-exposure reactive zone using the image analyzing software to determine the concentration of the at least one chemical species; optionally outputting the determined concentration of the at least one chemical species of the liquid medium; and optionally taking action based on the determined concentration.
Furthermore, WO 2015/036311 A1 disclose a method for determining the cleaning performance of a formulation, in which a) the formulation is provided, b) a test body is brought into contact with the formulation, the test body being contaminated with a protein-containing test contaminant, c) the contaminated test body is left in contact with the formulation in order to clean the contaminated test body, d) the cleaned test body is rinsed, e) if necessary the rinsed test body is dried, f) if necessary the test contaminant remaining on the test body is evaluated in terms of quality and g) the test contaminant remaining on the test body is analyzed in terms of quantity, the quantitative analysis of the remaining test contamination including the removal of the remaining test contaminant from the test body.
Nevertheless, albeit the existence of several monitoring alternatives, there is still the need for further processes, which can be used in the background of industrial working conditions and which are able to deliver reproducible results with a high sensitivity.